MadSci Network: Medicine

Re: Does the coating or type of pills effect it`s dissolving rate in the blood

Date: Thu Feb 5 09:46:16 2004
Posted By: Michael Maguire, Professor
Area of science: Medicine
ID: 1075605291.Me

Good question and good insight into advertising.  Don't believe everything 
you hear.

There are two issues here.

First, both the coating of a pill or the filler material that it is mixed 
with have an effect on how fast the pill dissolves and how fast the drug 
becomes soluble in the fluids in the small intestine.  The drug company 
can manipulate these to make a pill that dissolves very quickly or very 
slowly.  They can make multiple kinds of tiny, tiny pills for the same 
medicine, some that dissolve very slowly and some that dissolve very 
quickly.  These can then be mixed and put into a capsule (among other 
possibilities).  The result is that some of the medicine dissolves quickly 
and some slowly so that you have a longer time that the medicine is being 
circulated in your body.  For example, the drug Sudafed (aka 
pseudoephedrine) can be bought in the drug store in two different forms.  
It's used to dry up runny noses (a decongestant).  In one form, it 
contains 30 milligrams of drug that dissolves fast and is available to the 
body fairly quickly.  The other form has 120 milligrams but if made so 
that it dissolves slowly so that the higher dose is released over about 10-
12 hours.  This is supposed to provide long-term relief for your nose.  If 
you used only the smaller pill, you'd have to take one every 3-4 hours.  
With the slowly dissolving or "time-release" form of Sudafed, you take one 
pill every 12 hours.

Second, and more specifically to the advertising, most of the ads that say 
this or that medicine quickly dissolves and therefore gives your relief 
faster are really stretching the truth quite a bit.  I won't call the 
statement completely wrong but it is very deliberately misleading.  The 
simple fact is that most drugs dissolve pretty quickly in the stomach and 
small intestine, usually within 15 minutes.  Making sure they dissolve in 
5 min really doesn't change things very much.  The limiting factor is not 
how fast the drug dissolves but how fast the drug can be absorbed across 
the wall of the small intestine into the blood.  The speed at which a drug 
dissolves has absolutely no effect on how fast the drug can be absorbed by 
the intestine.  Perhaps, because a drug dissolves completely in 5 min 
instead of 15 min there would be more drug available to be absorbed in 
those first few minutes, but there's a limit on how fast the intestine can 
absorb the drug, so it doesn't make much of a practical difference.  At 
best, your headache might start going away in 10 minutes instead of 15 

As an additional point, drugs are NOT absorbed in the stomach.  They are 
absorbed virtually exclusively in the small intestine.  In some cases, you 
may not want the drug to dissolve quickly.  The stomach is very acid and 
could cause the drug to break down, and in a very few cases even injure 
the stomach.  The small intestine is much less acid and the drug won't 
break down there.  The absorption occurs in the small intestine simply 
because the total surface area of the small intestine is very, very large 
compared to the surface area of the stomach.  About 10,000 times greater.  
The speed at which a drug is absorbed is directly related to surface area, 
so most of the absorption occurs in the small intestine.

Current Queue | Current Queue for Medicine | Medicine archives

Try the links in the MadSci Library for more information on Medicine.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network,
© 1995-2003. All rights reserved.